FIELD OF THE INVENTION
The invention relates to a power semiconductor module, including at least one power semiconductor component fastened on a lead frame, at least partly encapsulated by a housing and electrically conductively connected to a plurality of output lines. The power semiconductor module has an interrupter irreversibly interrupting at least load current-carrying output lines and/or electrically conductive connections between the power semiconductor component and at least the load current-carrying output lines, in the event that the temperature of the power semiconductor component exceeds a predetermined temperature threshold.
When semiconductor components such as, for example, power switches are used, a fault or a failure can never be completely ruled out, which is the case, in principle, with all electrical devices. One possible fault situation is, for example, a so-called break-down or melt-through. In that case, for example in a high-side switch, a low-resistance connection is produced between the supply voltage source and the output terminal or, in the case of a low-side switch, a low-resistance connection of the output terminal to the device ground is produced. The electric current through the connected load circuit of the respective power switch can no longer be influenced by the driving logic configuration. Consequently, the load current is limited only by the resistance of the load in the load circuit.
In the event that the load likewise has a fault leading to short-circuiting of the load, the load current is limited only by the performance of the voltage supply and, consequently, by the internal resistance thereof. Consequently, a load current corresponding to the maximum current of the voltage supply permanently flows at the output of the power switch. That maximum load current typically causes uncontrolled heating of the power switch, which can cause a fire in the worst-case scenario.
A fuse, for example a thin resistance wire, is typically used as a precaution against such an occurrence. The fuses are connected into the load circuit between the supply voltage source and the semiconductor switch. The fuse interrupts the load circuit in the event of an excessively large current. In addition, a temperature sensor will typically be used which switches off the power switch in the event of excessive heating of the power switch that is caused, for example, by an excessively large load current or short-circuit current.
However, that precaution works only as long as the component is not defective.
U.S. Pat. No. 5,068,706 describes a three-phase rectifier having a fuse which melts in a defined manner if the semiconductor components exceed a predetermined temperature. That prevents the component from being destroyed.
However, the risk of the power switch having a low-resistance fault or short circuit, and at the same time the risk of the load to be switched likewise having a short circuit, is consciously accepted as an improbable double fault. If that double fault nevertheless occurs, the possible damage caused by a fire is disproportionately high and cannot be estimated.